I. Field of the Invention
The present invention relates to a tape transport wherein data is transmitted in the form of electrical signals between a stationary assembly and a rotating assembly of said transport. More specifically, the invention relates to the interface which effectuates data transfer between the assemblies.
II. Prior Art
The use of a rotating head device for recording and/or reproducing data from magnetic tape-like recording media is well known in the prior art. Generally a head wheel carrying one or more magnetic heads are positioned relative to a length of recording media. A thin film of air may or may not separate the media from the head wheel and the magnetic heads. However, in the type of device where the magnetic head/tape interface is separated by an air film the film is of sufficient thinness so as not to impede the recording and/or reproduction of data on/from the media.
To facilitate media support two mandrel halves are arranged in axial alignment to abut the rotating head wheel. The length of media which is associated with the rotating head wheel wraps the mandrel halves in a helical manner for support. As the magnetic heads are rotated in a circular orbit by the head wheel closely adjacent oblique data tracks are recorded on the media. Alternately, if the apparatus is in a reproduction mode pre-recorded data are reproduced from the oblique tracks. More detailed discussion of the above described rotating head device may be found in U.S. Pat. Nos. 3,845,500, issued to Gary Hart and assigned to IBM; 3,867,725, issued to Donovan M. Janssen et al., and assigned to IBM; 3,823,415, issued to Gene A. Fisher et al. and assigned to IBM and 3,840,894, issued to P. J. Arseneault and assigned to IBM.
In order to transmit data, in the form of electrical signals, from the rotatable head wheel to the stationary portion of the tape transport sliding ring contacts also known as slip rings, with contact brushes or else mercury contacts are used in the prior art. However, due to machine failure, interference, and maintenance problems the use of the afore-mentioned type of transmission interface has been discontinued for the transmission of high speed electrical signals. Instead internal inductive repeaters or transformers are used almost exclusively.
One type of transformer includes magnetic cores with annular windings, said cores are disposed in pairs concentrically and in space relationship with each other whereby one core is secured to a rotatable portion and the associated core is secured concentrically thereto on a fixed portion of the device or tape transport. Each pair of annular cores transmit signals to magnetic head or heads positioned on the rotor. Each of the annular cores has a coil or winding positioned in a single groove, machined into the core. A general discussion of this type of concentric transformer is given and shown in U.S. Pat. No. 3,763,327.
The present invention relates to a concentric transformer of this type.
Although the prior art concentric transformer operates satisfactorily for its intended purposes it has several shortcomings which the present invention will improve significantly.
One of the drawbacks with the prior art concentric transformers is that the transformers are expensive and very difficult to assemble. This drawback stems from the fact that in order to fabricate a prior art transformer a Printed Circuit (P.C.) coil is manufactured from a plurality of separate strands of copper wire. The strands of copper wire are laid down on a clear mylar backing using conventional P.C. technique. In order to form a continuous wire or coil the strands have to be soldered end to end, respectively. The desired number of turns is then fabricated from the continuous strand to form a coil and the coil is positioned within a groove machined within the periphery of the core. The task of soldering the individual strands is laborious, time consuming and therefore significantly increases the cost of the transformer.
As will be explained subsequently in describing the present invention, unless the aforementioned laborious method is practiced in manufacturing the coil, the fabricated transformer may not function in a satisfactory manner. Additional information on the aforementioned coil design may be obtained from an article entitled "Printed-Circuit Winding for Concentric Transformer", published in IBM Technical Disclosure Bulletin, Vol. 18, No. 1, June 1975, p. 47.
Another drawback with the prior art transformers is that said transformers arre susceptible to interference both as a radiating source and as a receiving source. To alleviate this problem shielding is required. Alternately, an optimum distance sufficient to reduce crosstalk has to be maintained between adjacent transformer pairs. As is well known to those skilled in the art in a rotating head device there is very little room for either shielding or spacing the separate transformers to reduce interference. As a result the performance of device using the prior art transformers is somewhat degradated.